1. Field of the Invention
The present invention relates to a driving wheel bearing unit which comprises a drive train of a motor vehicle. In particular, the prevent invention relates to a driving wheel bearing unit in which a wheel bearing for supporting a driving wheel of a motor vehicle is integrated with a constant velocity joint that establishes coupling with a driving shaft for transmitting power to the driving wheel.
2. Description of the Related Art
As shown in FIGS. 9 and 10, this type of wheel bearing unit includes a driving shaft 1 which is coupled at its inner end to a differential 3 via a slide type constant velocity joint 2 and at its outer end to a wheel bearing 4 via a rigid type constant velocity joint 14. Here, the inner end of the driving shaft 1 refers to the end on the inside when viewed in the direction of width of a car body (the right sides in FIGS. 1-6, 9, and 10). Then, the outer end of the driving shaft 1 refers to the end on the outside when viewed in the direction of width of the car body (the left sides in FIGS. 1-6, 9, and 10). The wheel bearing 4 comprises an external member 11 and an internal member 13. The external member 11 is fixed to a knuckle 10 which is supported by the car body via a suspension system. The internal member 13 is rotatably supported inside the external member 11 via two rows of rolling elements 12a and 12b. An outside joint member 15 of the constant velocity joint 14 is coaxially coupled to and integrated with the internal member 13.
The knuckle 10 has a circular mounting hole 10a drilled therethrough in the car width direction. The external member 11 has a cylindrical outer periphery 11a at one end and a flange 11b at the other. The outer periphery 11a of the external member 11 is fitted to the mounting hole 10a in the knuckle 10. Then, mounting bolts 21 are inserted through bolt holes in the knuckle 10 from inside, and screwed into a plurality of screw holes 11c formed in the flange 11b. This fastens the knuckle 10 and the external member 11 to each other. Outer races 11d and 11e for the two rows of rolling elements 12a and 12b are formed in the inner periphery of the external member 11. Of two inner races corresponding to these outer races, one 13c is formed in the outer periphery of the internal member 13, and the other 15a is formed in the outer periphery of the outside joint member 15 of the constant velocity joint 14.
The constant velocity joint 14 is chiefly composed of the outside joint member 15, an inside joint member 16, a cage 17, a plurality of torque transmission balls 18, and a boot 19. The outside joint member 15 consists of a bowl-like mouth part and a shaft-like stem part. The mouth part has a spherical inner periphery provided with six guide grooves which extend along the axial direction at regular circumferential intervals. Formed on the stem part are a shoulder portion 15b extending perpendicularly to the axis, a press-in portion 15c having a cylindrical outer periphery, a spline shaft portion 15d, and a caulking portion 15e. These portions 15b-15e are arranged in series on the shaft-end side of the above-described inner race 15a. The inside joint member 16 has a spherical outer periphery provided with six guide grooves which extend along the axial direction at regular circumferential intervals. The outer end of the driving shaft 1 is spline-connected to this inside joint member 16. The guide grooves in the outside joint member 15 and the guide grooves in the inside joint member 16 are paired to form six ball tracks, in which six torque transmission balls 18 are arranged, i.e. one in each ball track, to make torque transmission between both the joint members. The cage 17 for retaining the torque transmission balls 18 is interposed between the inner periphery of the outside joint member 15 and the outer periphery of the inside joint member 16. The boot 19 of accordion form is fixed at its larger end to the outer periphery of the mouth part of the outside joint member 15. The smaller end of the boot 19 is fixed to the outer periphery of the driving shaft 1.
A flange 13a intended for wheel mounting is integrally formed on the outer periphery of the internal member 13. Hub bolts 22 are fixed to the flange 13a at a plurality of positions along the circumferential direction. The internal member 13 is shaped like a hollow cylinder, having a cylindrical hole portion and a spline hole portion 13b to be fitted to the outside joint member 15. The press-in portion 15c of the outside joint member 15 is pressed into the inner periphery of the internal member 13, and the spline shaft portion 15d of the outside joint member 15 is spline-connected to the spline hole portion 13b of the internal member 13. Then, with the shoulder portion 15b pressed against the inner end of the internal member 13, the caulking portion 15e is caulked with the outer end of the internal member 13 to integrate the internal member 13 and the outside joint member 15 with each other.
In the wheel bearing unit described above, the maximum outer diameter of the constant velocity joint 14, especially of the boot 19, is greater than the inner diameter of the mounting hole 10a in the knuckle 10. Accordingly, there has been a necessity to assemble the constant velocity joint 14 and the wheel bearing 4 on carmaker side, meaning poor workability. Besides, when the wheel bearing 4 and constant velocity joint 14 mounted on a car body are to undergo inspections, repairs, and the like, and when the constant velocity joint is to undergo boot replacement in particular, it has been needed that the entire unit including the knuckle 10 be dismounted from the car body, resulting in poor workability.
An object of the present invention is to facilitate the disassembly, assembly, and other works on a driving wheel bearing unit.
The present invention has solved the foregoing problem by rendering the diameter of the constant velocity joint across its maximum diameter portion equal to or smaller than the diameter of the external member across the fitting surface thereof.
In general, the maximum outer diameter portion of a boot attached to the outer periphery of the outside joint member makes the maximum diameter portion of the constant velocity joint. Therefore, when the diameter of this boot""s maximum outer diameter portion is set to be equal to or smaller than the diameter of the external member across the fitting surface, it becomes possible to pass the entire constant velocity joint through a mating member to be fitted to the fitting surface of the external member, i.e., the mounting hole in the knuckle.
According to the present invention, it becomes possible to mount a wheel bearing and a constant velocity joint to a knuckle after assembly, with an improvement in workability. For example, when the wheel bearing and the constant velocity joint are mounted to a car body, their preassembly can be inserted from outside the car body to a mounting hole in the knuckle for mounting. When they are dismounted from the car body, the fastening between the external member and the knuckle can be released to allow the unitary extraction of the wheel bearing and the constant velocity joint from the mounting hole in the knuckle. This facilitates works including inspections and repairs.
More specifically, a driving wheel bearing unit is provided comprising: a wheel bearing including an external member having an outer periphery provided with a mounting flange for car-body mounting and a fitting surface, and an inner periphery provided with two outer races, and an internal member rotatably arranged inside the external member via a rolling element, the internal member having an outer periphery provided with a race and a wheel mounting flange for mounting a wheel; and a constant velocity joint to be arranged on one end of a driving shaft, the constant velocity joint including an outside joint member having an inner periphery provided with eight guide grooves, an inside joint member having an outer periphery provided with eight guide grooves, eight torque transmission balls individually arranged in eight ball tracks formed by pairs of the guide grooves in the outside joint member and the guide grooves in the inside joint member, a cage for retaining the torque transmission balls, and a boot to be attached to the outside joint member; the wheel bearing and the outside joint member of the constant velocity joint being integrated with each other. Here, the diameter of the boot across its maximum diameter portion is made equal to or smaller than the diameter of the external member across the fitting surface.
Alternatively, in the cases of using a boot apt to elastic deformation such as a rubber boot, the boot can be passed through the mounting hole in the knuckle as deformed elastically. Therefore, it is required only that the maximum diameter portion of the outside joint member have such a diameter as to pass through the mounting hole in the knuckle. Thus, the maximum diameter portion of the outside joint member is sometimes regarded as the maximum diameter portion of the constant velocity joint.
More specifically, a driving wheel bearing unit is provided comprising: a wheel bearing including an external member having an outer periphery provided with a mounting flange for car-body mounting and a fitting surface, and an inner periphery provided with two outer races, and an internal member rotatably arranged inside the external member via a rolling element, the internal member having an outer periphery provided with a race and a wheel mounting flange for mounting a wheel; and a constant velocity joint to be arranged on one end of a driving shaft, the constant velocity joint including an outside joint member having an inner periphery provided with eight guide grooves, an inside joint member having an outer periphery provided with eight guide grooves, eight torque transmission balls individually arranged in eight ball tracks formed by pairs of the guide grooves in the outside joint member and the guide grooves in the inside joint member, a cage for retaining the torque transmission balls, and a boot to be attached to the outside joint member; the wheel bearing and the outside joint member of the constant velocity joint being integrated with each other. Here, the diameter of the outside joint member across its maximum diameter portion is made equal to or smaller than the diameter of the external member across the fitting surface
A constant velocity joint using eight torque transmission balls may have an outside joint member of smaller outer diameter as compared with a conventional constant velocity joint with six balls. Therefore, in rendering the maximum diameter portion of the constant velocity joint equal to or smaller than the fitting surface of the external member in diameter, optimum design can be made without affecting other specifications such as the strength of the constant velocity joint.
The wheel bearing, the constant velocity joint to be arranged on the one end of the driving shaft, the driving shaft, and a constant velocity joint to be arranged on the other end of the driving shaft may constitute a drive shaft assembly in which and the maximum outer diameter of the drive shaft assembly is made equal to or smaller than the diameter of the external member across the fitting surface.
One of two inner races corresponding to the two outer races on the external member may be arranged in the outer periphery of the internal member, and the other in the outer periphery of the outside joint member.
The internal member of the wheel bearing and the outside joint member of the constant velocity joint may be integrated with each other by staking. Here, fastening with a nut may also be adopted as the means for connecting the two parts. Nevertheless, the integration by staking makes separation difficult, and hence maximizes the advantage of the present invention that the entire wheel bearing unit can be mounted on and dismounted from the knuckle in the form of an assembly.
The constant velocity joint to be arranged on the other end of the driving shaft may comprise: an outside joint member having a cylindrical inside surface provided with eight linear guide grooves extending axially; an inside joint member having a spherical outside surface provided with eight linear guide grooves extending axially; eight torque transmission balls individually arranged in eight ball tracks formed by pairs of the guide grooves in the outside joint member and the guide grooves in the inside joint member; and a cage for retaining the torque transmission balls.
The boot may be made of resin material.